After Deputy Attorney General Rod Rosenstein announced today that Special Counsel Robert Mueller had obtained grand jury indictments against thirteen Russians who conspired to rig the election in Donald Trump’s favor, Trump fired back by claiming the indictments exonerated him. It took just a few hours for Mueller to fire back through the media, setting the record straight.

According to the indictments, the Donald Trump campaign was not knowingly colluding with these thirteen Russians in particular. Trump seized the opportunity to misrepresent this, promptly tweeting “The Trump campaign did nothing wrong – no collusion!” But that’s not even close to being true. Donald Trump Jr has been caught admitting in emails that he knowingly conspired with the Russian government to try to alter the outcome of the election. Several other top Trump advisers were in that same meeting, or held similar meetings or exchanges with the Russians.

Robert Mueller has rarely spoken in this investigation, never in his own voice, and only occasionally through the media. So it’s notable that, less than an hour after Trump’s misleading tweet, Mueller got word to the media that he is in fact still investigating Trump-Russia collusion (link). To be clear, “collusion” isn’t a legal term. The question here is whether Trump and his people broke specific laws by conspiring with the Russians to alter the outcome of the election. We already know the answer is “yes.” Mueller will prove it.

But the noteworthy part today is that Robert Mueller wasn’t willing to allow Donald Trump’s lying tweet to stand on its own. On a day in which Rod Rosenstein, the guy in charge of the Mueller investigation, made a point of holding a press conference just to make sure these Russian indictments got enough visibility, Mueller then made sure that that Trump’s false claim of “no collusion” got promptly struck down. Mueller isn’t just playing offense now; he’s increasingly doing it in public.